Abstract— Sustainable wastewater treatment is getting more attention worldwide. Researchers have been looking for cost effective and environment friendly technologies at the same time. For fish wastewater, nitrogen discharge limit is very high because of the regular fish-food leftover and wastes from fish. In this study, different types of biological filter media were used to host and grow nitrifying bacteria. The media made from biomass ash and coal bottom ash were tested in laboratory water treatment units in comparison with commercial media in terms of nitrogen compound removal. Under a given test condition of water temperature ranging from 26 0 C to 28 0 C and DO >4.00 mg L -1 , the media made from biomass ash showed superior removal of nitrogen compounds and the toxic nitrogen wastes were removed within 16 days. In addition, scanning electron microscopic examination revealed that microstructural features of these media were suitable for growth of nitrobacteria, leading to improving nitrification performance. Keywords— Biological treatment, Aerobic biological filter, Coal bottom ash, Porous pellets. I. INTRODUCTION Pollution related problems have become more attentive worldwide. Fish wastewater is an imperative source of water pollution. Normally it consists of oil and grease, salt and ammonia [1]. Biological treatment for removal of nitrogen waste is mainly focused among different treatment processes. Filter media are essential for this process, providing high surface area for bacteria to grow sufficiently for the reduction of toxic nitrogen compounds [2]. With the presence of functional micro organism, ammonia discharged to the system will be converted to nitrite (NO 2 - ) and finally nitrate ion (NO 3 - ). This is called nitrification process [3]. The basic chemical conversions occurring this process by Nitrosomonas and Nitrobacter are expressed by, NH 4 + + 1.5O 2 → NO 2 - + 2H + + H 2 O NO 2 - + 0.5O 2 → NO 3 - At very low oxygen concentration, some species of functional bacteria utilize the oxygen in nitrate and convert it to nitrogen gas (N 2 ). This process is called denitrification. Tahmina Sultana (Corresponding Author), Kasetsart University (KU), Bangkok, Thailand. Email: [email protected]Penjit Srinophakun (Author), Kasetsart University (KU), Bangkok, Thailand. Email: [email protected]Umaporn Sanewirush and Pakamard Saewong (Author), National Metal and Materials Technology Center (MTEC), NSTDA, Thailand. Email: [email protected]Compared with the regular biological nitrogen removal (nitrification- denitrification) process, biological filtration process is an energy-efficient and sustainable wastewater treatment technology [4]. Pumice as well as porous materials from nature, are being used widely and available in the market. In this study, pellets prepared from rice husk ash (RHA) and coal bottom ash (CBA) are introduced as alternatives of those conventional media. These porous media are characterized and compared their effectiveness on nitrogen compound removal with the commercially available pumice. II. EXPERIMENTAL PROCEDURE A. Media Preparation The research was conducted at the Pilot plant of National Metal and Materials Technology Center (MTEC), NSTDA, Thailand. RHA and CBA media were prepared from RHA and CBA by mixing a ready mix ash precursors with water, shaping and firing at around 1100 0 C for 1hour [5] while pumice was purchased from the market, crushed and size selected to 4-12mm. B. Testing Unit Setup To prepare a recirculation water flow system, a 2 and 27 liter plastic boxes were used as a media container and a water tank, respectively. The water was circulated by a pump, which was fixed at the bottom of the water tank, to the media container and returned to the tank via PVC pipes (Fig. 1). 4 different sets were prepared for this study: 1) with RHA, 2) CBA 3) pumice and 4) without media. Each set had 4 duplicates. Every water tank of each duplicate was filled with 20 liters of water and the set with media was added with 1 liter of media. C. Material Characterization Density of the media was measured by Achimedes’ method. While for the micro-structural observation, the samples were gold coated and examined in a scanning electron microscope (SEM). Surface area of each media was estimated by measuring the pore size at the surface of the media and using spherical equivalent method. Comparison of Biological Wastewater Treatment Ability of Filter Media Made From Biomass Ash Tahmina Sultana, Penjit Srinophakun, Umaporn Sanewirush and Pakamard Saewong Int’l Journal of Advances in Chemical Engg., & Biological Sciences (IJACEBS) Vol. 4, Issue 1 (2017) ISSN 2349-1507 EISSN 2349-1515 https://doi.org/10.15242/IJACEBS.A0217031 108
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Abstract— Sustainable wastewater treatment is getting more
attention worldwide. Researchers have been looking for cost effective
and environment friendly technologies at the same time. For fish
wastewater, nitrogen discharge limit is very high because of the
regular fish-food leftover and wastes from fish. In this study,
different types of biological filter media were used to host and grow
nitrifying bacteria. The media made from biomass ash and coal
bottom ash were tested in laboratory water treatment units in
comparison with commercial media in terms of nitrogen compound
removal. Under a given test condition of water temperature ranging
from 260C to 280C and DO >4.00 mg L-1, the media made from
biomass ash showed superior removal of nitrogen compounds and
the toxic nitrogen wastes were removed within 16 days. In addition,
scanning electron microscopic examination revealed that
microstructural features of these media were suitable for growth of
nitrobacteria, leading to improving nitrification performance.